Located south of the village of Wendover in Buckinghamshire, the 450-metre-long viaduct will be the first major railway bridge in the UK to be built with a double composite structure, using less carbon-intensive concrete and steel in comparison to a more traditional design.
It will be made from two steel girders sandwiched between two layers of reinforced concrete for maximum strength and minimum weight.
As previously reported, this design has been calculated to save an 7,433 tonnes of embodied carbon within materials.
Over the summer, engineers working for contractor EKFB – a team made up of Eiffage, Kier, Ferrovial Construction and Bam Nuttall – will sink 53 concrete piles to form the foundations for the structure.
On top of each group of piles – which will range from between 38 and 46 metres deep – a concrete pile cap will support the pier, which will in turn support the weight of the bridge structure above. Instead of hammering the piles into the ground, holes will be bored before being backfilled to create the pile.
The piers – some of which will be up to 14 metres high – will be cast as shells before being assembled on site and filled with concrete. This approach is expected to reduce the amount of work on site and cut disruption for local residents. The first double composite beams will be installed next year.
HS2 Ltd project client Rohan Perin said: “Concrete is one of the construction industries’ biggest sources of embedded carbon – and this innovative design will help us cut our carbon footprint while delivering a lighter, stronger and more elegant structure.”
EKFB worked with design partner ASC (a joint venture between Arcadis, Setec and Cowi) and specialist architect Moxon on the double composite, approach, which was inspired by structures on the French high speed TGV network.
EKFB senior engineer James Collings said: “The team has worked hard to deliver the preparatory works ahead of this stage. We’ve also been busy constructing the pier platform for the north side of the viaduct. The Wendover Dean Viaduct will sit narrowly between two hills, spanning 450 metres across, and its design is pioneering, conveying a lightweight structure benefiting from less concrete and steel being used in the construction process.”
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